A drop-on-demand ink-jet head is known as an ink-jet head that can eject, in response to the input signal, required amounts of ink droplets only when they are needed to print on the medium. In particular, extensive research is being undertaken on the piezoelectric (piezo) drop-on-demand ink-jet head since it is capable of well controlled ejection of a wide variety of inks. The drop-on-demand piezoelectric ink-jet head generally includes an ink supply channel, multiple pressure chambers, each of the pressure chambers has a nozzle and is connected to the ink supply channel, and piezoelements for applying pressure to ink filling the pressure chamber.
In the piezoelectric ink-jet head, piezoelectric elements deform by application of a drive voltage, whereby a pressure is applied to the ink in the pressure chamber, causing ink droplets to be ejected through nozzles. Broadly, there are three types of piezoelectric ink-jet head according to the manner in which the piezoelectric elements deform: share-mode, push-mode, and bend-mode. In particular, because of its ability to produce high power at low voltage, the bend-mode piezoelectric ink-jet head using multilayer piezoelements is expected to be further developed for use in manufacture of electronic devices such as organic EL displays and liquid crystal panels (for example, see Patent Literature 1).
Ink jet heads sometimes encounter the problem of failing to accurately eject ink droplets due to air inclusion or nozzle clogging. To overcome the above problem, a technique is known where an ink-jet head includes an ink discharge channel that communicates with pressure chambers and is configured to allow ink discharged from the pressure chambers to flow in order to feed ink from an ink supply channel to the ink discharge channel via the pressure chambers to circulate the ink (for example, see Patent Literature 2).
FIG. 1 is a schematic diagram of an ink-circulating ink-jet head disclosed in Patent Literature 2. As shown in FIG. 1, the ink-jet head disclosed in Patent Literature 2 includes ink supply channel 10, ink discharge channel 11, and pressure chambers 12A to 12C. Each of pressure chambers 12A to 12C communicates with ink supply channel 10 and ink discharge channel 11. In other words, pressure chambers 12A to 12C communicate with ink supply channel 10 via communication ports 16A to 16C, respectively, and communicate with ink discharge channel 11 via communication ports 17A to 17C, respectively. Further, actuators 13A to 13C are arranged in pressure chambers 12A to 12C, where nozzles 14A to 14C are formed, respectively.
As shown in FIG. 1, ink is supplied from ink supply port 50 and flows in ink supply channel 10 to be supplied to pressure chambers 12A to 12C. Part of the ink supplied to pressure chambers 12A to 12C is ejected as droplets through nozzles 14A to 14C by an action of actuators 13A to 13C, respectively, and the remaining ink is supplied to ink discharge channel 11 to be discharged from ink discharge port 51.
By feeding the ink from the ink supply channel to the ink discharge channel in this way, new ink is constantly supplied to the pressure chambers, preventing the problem of failing to accurately eject ink droplets due to air inclusion or nozzle clogging.
Further, a technique is known where an ink-jet head includes an ink common chamber (ink supply channel) having unevenness on an inner surface of the ink common chamber in order to prevent a pressure wave in the pressure chamber generated by an action of the actuator from propagating in the ink common chamber to affect another pressure chambers (for example, see Patent Literatures 3 to 5). By providing the unevenness on the inner surface of the ink common chamber in this way, a pressure wave propagated from pressure chambers to the ink common chamber can be attenuated. Further, a technique is known where unevenness is provided in the ink common chamber from a viewpoint of reducing the number of the actuators in the ink common chamber (for example, see Patent Literatures 6 and 7). Further, a technique of providing unevenness in the pressure chambers is also known to prevent bubbles from reaching the nozzles (for example, see Patent Literatures 8 and 9).